Rotary hook for sewing machines



Feb. 15 1938.

G. SAUER ROTARY HOOK FOR SEWING MACHINES INVENTOR. qeorga Samar, BY Q W I ATTORNEYS.

Filed Jan. 25, 1956 PatentecIFeb. 15, 1938 ROTARY HOOK FOR SEWINGJ/[AQHINES George Sauer, Berwyn, Ill, assignor to Union Special Machine Company, Chicago, 111., a corporation of Illinois Application January 25, 1936, Serial No. 60,766

4 Claims.

This invention relates to rotary hooks for lock stitch sewing machines; and it has more especial reference to that type of rotary hook wherein the revolving hook member has a substantially 5 continuous circumferential tongue and groove connection with the stationarily held bobbin case. The interengaging surfaces of the revolving hook member and the bobbin case of such a rotary hook are thus of considerable area, as a result of which a large amount of heat is generated by friction between them, particularly when the sewing machine is operated at high speeds. Under this condition, the wear of the hook parts is extremely rapid, and they must therefore of necessity be frequently renewed, with attendant loss of the time required in effecting the replacements, and with curtailment in the output from the sewing machines.

My invention has for its aim to offset as far as possible the drawbacks which have been pointed out. This objective I realize in practice, as here inafter more fully set forth, through provision of an improved construction wherein the interengaging surfaces of the revolving hook member 5 and the bobbin case contact only in areas of relatively small size, with the result that the friction between them is very materially reduced and the vulnerability to rapid wear, even at speeds heretofore considered excessive, substantially obviated.

In the drawing, Fig. I is a view, partly in elevation and partly in axial section, of a rotary hook conveniently embodying my invention.

Fig. II is a transverse section taken as indicated by the arrows II-II in Fig. I; and

Fig, III is a'perspective view of the stationary member or bobbin case of the rotary hook.

The rotary hook which I have herein illustrated to exemplify my invention is generally of well 40 known construction, comprising a bobbin case I;

and a revolving member 2 with a needle loop engaging hook 3 mounted to rotate about the bobbin case I. As usual, the hook member 2 is formed with a rearwardly-extending axial hub 4 by which 5 it is secured to the end of a drive shaft 5 with the aid of set screws shown at 6. Also after common practice, the revolving hook member 2 is provided with an internal circumferential groove I; but the bobbin case I, instead of. having, as

50 ordinarily, a substantially continuous peripheral tongue to engage the groove I, is formed in accordance with my invention, with a tongue which is interrupted, as at 8, at a plurality of circumferentially-spaced points. It is to be particularly 5 observed that the interruptions or voids .8, of

to be understood that it may be varied if desired which there are six in the present instance, are comparatively wide circumferentially of the bobbin case I, and that they define a series of peripheral projections 9, which, except for the one indicated at if] which plays an important part in 5 the release of a needle loop from the bobbin case at the usual loop clearing interval II, are very small relatively. As shown, these projections 9 engage the groove I of the rotary hook with a snug working fit for the purposes of a bearing 10 capable of resisting am'al thrust of said hook in both directions.

As a consequence of the described construction, the rib on the bobbin case I has, for the most part, spot contact only with the walls of the 15 groove 7 in the revolving hook member 2. It therefore follows that the friction between the parts and the heat generated during the functioning of the rotary hook is correspondingly reduced. In view of this fact, and, moreover, since 20 cooling, air is allowed to circulate more freely through the intervals 8 and around the contacting portions of the bobbincase I and the revolv 7 ing hook member 2, a sewing machine equipped total surface area of the groove I in the revolving member 2. While this proportioning has given very excellent results in practice, it is of course or found expedient.

It is to be further understood that my invention is to be regarded as comprehensive of all modifications possible within the scope of the appended claims.

Having thus described my invention, I claim: 1. In combination, a rotary hook, and a bobbin case about which the hook revolves, the one having a circumferential groove, and the other having a series of small circumferential projections extending substantially all the way around it and engaging the groove with a working fit, said projections being spaced by intervals great enough to materially reduce the friction and heating tendencies of the hook and the bobbin case.

2. In combination, a rotary hook, and a bobbin case about which the hook revolves, the one having a circumferential groove, and the other having a series of small circumferential projections extending substantially all the way around it and engaging the groove with a working fit, said projections being spaced by intervals great enough to materially reduce the friction and heating tendencies of the hook and the bobbin case, and their aggregate contacting surface being less than half the total surface area of the groove walls.

3. In combination, a rotary hook with an internal circumferential groove and a bobbin case about which the hook revolves, said case having a series of small projections extending substantially all the Way around its periphery and engaging the groove of the hook with a working fit,

said projections being spaced by intervals great enough to materially reduce the friction and heating tendencies of the hook and the bobbin case.

4. In combination, a rotary hook with an internal circumferential groove and a bobbin case about which the hook revolves, said case having a series of small projections extending substantially all the Way around its periphery and engaging the groove of the hook with a working fit, said projections being spaced by intervals great enough to reduce the friction and heating tendencies of the hook and the bobbin case, and their aggregate contacting surface area being less than half the total surface area of the groove walls.

GEORGE SAUER. 

